1. Field of the Invention
The invention relates to a lighting device, and more particularly to automotive/vehicular lighting devices such as headlamps, auxiliary headlamps, and various lamps that are arranged in front parts of a motor vehicle. In addition, the invention relates to illuminating lights for use in lighting fixtures such as traffic lamps, household lamps, general vehicle lamps, etc.
2. Description of the Related Art
FIGS. 1 and 2 show examples of configurations of conventional lighting devices. The lighting device 1 shown in FIG. 1 is composed of a light source 2, a projection lens 3 for focusing the light from the light source 2, and a distribution control member 4 arranged in front of the projection lens 3.
The light source 2 is a near point-like light source, such as an LED. When a drive voltage is applied thereto, the LED emits light to a predetermined range of angles about its optical axis perpendicular to a mounting board 2a. 
The projection lens 3 is made of a convex lens. This convex lens is configured so that its source-side focus lies near the light source 2, and its optical axis coincides with that of the light source 2.
The distribution control member 4 is a plate-like transparent member, for example, which has lens-cut prisms for light diffusion on one of its surfaces (in the case shown in FIG. 1, the lens-cut prisms are provided on the source-side bottom surface).
In the lighting device 1 thus configured, light emitted from the light source 2 is incident on the projection lens 3. The light is focused by the projection lens 3 into near parallel light, which is incident on the distribution control member 4. The light incident on the distribution control member 4 is then diffused by the distribution control member 4 as appropriate, given a desired light distribution characteristic, and is projected toward the front.
Turning now to FIG. 2, a lighting device 5 is composed of a light source 2, a reflecting surface 6 for reflecting light from the light source 2 toward the front (upward in the diagram), and a projection lens 7 for focusing the light from the reflecting surface 6.
The reflecting surface 6 is made of an elliptic reflecting surface, for example, which is situated so that a first focus thereof lies near the light source 2 and its major axis coincides with the optical axis of the light source 2. The projection lens 7 is made of an aspheric lens. This aspheric lens is situated so that its source-side focus lies near a second focus of the reflecting surface 6 and its optical axis coincides with that of the light source 2.
In the lighting device 5 thus configured, the light emitted from the light source 2 is reflected by the reflecting surface 6 and incident on the projection lens 7. Then, the light is focused by the projection lens 7 as well as controlled in distribution based on the aspheric configuration of the same. As a result, the light is projected toward the front with a predetermined light distribution characteristic.
The foregoing lighting devices 1 and 5, however, have had the following problems.
That is, in the lighting device 1, obtaining a desired light distribution characteristic requires the two optical members, i.e., the projection lens 3 and the distribution control member 4. The light transmittances of these optical members thus have an effect on this optical system, increasing the transmission loss of the light. These optical members can cause additional problems in accuracies, such as a positional accuracy and a tilt accuracy with each other. In addition, the large dimension in the direction of the optical axis also produces the problem of an increase in total weight.
With the lighting device 5, the use of the reflecting surface 6 can make the light transmission loss smaller than in the lighting device 1. Nevertheless, since the reflecting surface 6 is arranged behind the light source 2, there have also been problems in that the device requires a large dimension in the direction of the optical axis and has an increased total weight.
Furthermore, the lighting devices 1 and 5 are both round in appearance. This leads to stereotypical designs with fewer variations in appearance. Since it is difficult and sometimes impossible to provide functional three-dimensional appearances, there have been problems with poor merchantability and design novelty.